Overview
In the cat the clavicle (clavicula) is a vestigial bone: a thin, slightly curved rod lying cranial to the shoulder joint. Unlike the human clavicle it forms no joints with the sternum or the scapula; it is embedded in the muscles and held only by connective tissue. It is better developed and more consistently ossified in the cat than in the dog, where it is usually a small cartilaginous nodule or is absent.
Relations
- It lies in the clavicular intersection of the brachiocephalicus muscle, the tendinous band that separates its parts. In the cat the parts of this muscle are described as the cleidobrachialis (to the humerus), the cleidocervicalis (to the neck) and the cleidomastoideus (to the mastoid region of the skull), all anchored on the clavicle.
- Without an articulated clavicle the scapula is joined to the trunk only by muscles (synsarcosis). This lets the shoulder move freely, lengthens the stride and cushions the impact on the thoracic limbs when landing.
Clinical relevance
- Radiography: it appears as a small linear bony shadow cranial to the shoulder joint and the manubrium, especially on ventrodorsal views. It is a normal structure and must not be mistaken for a foreign body or a fracture fragment.
- Surgery: it may be found when dissecting the cranial muscles of the shoulder and neck.
In this model the clavicle is illustrative geometry added by hand; its shape and position are approximate.